The «Furnace» for the Lunokhod.

The heavy automatic station Luna 17 softly landed on the surface of the Moon 50 years ago. EDB Fakel from Kaliningrad was involved in the Lunokhod engineering works in a co-operation.  

A day on the Moon lasts for as long as its night and is equal to 14.75 of the Earth days. The absence of atmosphere and a slow rotation lead to a huge temperature difference on one and the same area of the lunar surface. On the sunny side of the moon temperature can reach +130°С and decrease down to -170°С at night. According to the technical development specification, the rover vehicle was to “survive” 3 lunar days. To secure the operability of the equipment embedded in a pressurized container, the container had to be thermally controlled in the range of 0…40°С to prevent from being turned cold or overheated. As a heat source it was decided to use a radioisotope heater with a power higher than 1 kW at the beginning of the operation. The head organization Zarya was assigned to the heater development and manufacturing.

Kaliningrad-based EDB Fakel was also involved in the Lunokhod engineering works in a co-operation. The bureau was responsible for manufacturing and testing of a heat exchange unit for the isotope heat source. Yu.P.Mosalev was assigned as the theme leader. He named this product the “Furnace”. This name turned out to be so good that it was used not only in everyday speech but was also defined in the technical documentation.

The heat exchange unit was a two-way cylindrical apparatus with an isotope heat source placed inside. Gaseous nitrogen, which was heated in the heat exchanger, was supplied to the Lunokhod instrument compartment through the pressurized pipework with the help of a fan blower. Polished gold-plated gates for gas circulation regulation were installed in the gas lines at the inlet and outlet of the heat exchanger. At a sunny day the gates were supposed to be closed to emit the heating power from the “Furnace” heaters, while they were opened at a lunar night to heat the equipment located in the pressurized container.

When manufacturing the “Furnace” it was necessary to ensure that the heat exchange unit and gas contour are highly leak-proof, the design is resistant to temperature variations up to 300°С, external surfaces thermal emissivity is stable and flow path of the heat exchange unit has proper gas and dynamic characteristics. The mass and dimensional limitations were certainly to be respected. More than 40 various variants had been produced and tested before making a flight sample of the “Furnace”. These variants were rejected for different reasons. Being a crucial assembly unit of the spacecraft the “Furnace” was supposed to pass a full set of tests including a simulation of mechanical loads at the lift-off of the launcher and a simulation of temperature conditions while staying on the Moon.

On 17 November 1970 the spacecraft settled to the Moon in the Sea of rains. A months-long journey full of discoveries began. The thermal regulating system worked flawlessly throughout the expedition. According to the telemetry data, a comfortable temperature was maintained in the instrument compartment in the range of +7…+32°С. The last communication session took place on 14 September 1971. The Lunokhod-1 didn’t survive the 11th lunar winter. Due to the power decrease of the isotope heater source the heat release from the “Furnace” lowered by almost 4 times, what led to the equipment overcooling. By that moment of time the rover had traveled 10.5 km with its cumulated operational time equal to 301 days. This value fatally matched the duration of its life test that was performed at the enterprise. The active lifetime of the Lunokhod-1 exceeded the specified lifetime by 3 times.

The Roscosmos state corporation presents a new series of declassified materials about the development and launch of this unique spacecraft. The selection contains ministerial and institutional documents, minutes of the production meetings, reporting documentation and fragments of correspondence between the works participants and rocket-space industry authority.

JSC EDB Fakel (a part of the state corporation Roscosmos) is one of the leading enterprises in development of electric propulsion systems and thermal catalytic propulsion systems operating using Hydrazine. Fakel has a production experience in serial and mass delivery of thrusters both in commercial and state market segments. The share of the thrusters production in the world for spacecraft is about 10%. More than 70 Russian spacecraft (more than 60% of the Russian orbital constellation) and 30 Western spacecraft are equipped with thrusters developed and produced by EDB Fakel. Today EDB Fakel’s partners are ISS Reshetnev, RSC Energia, Khrunichev State Research and Production Center, Lavochkin Research and Production Association, Research and Production Corporation VNIIEM, Maxar (USA), Airbus, TAS (France), MELСO (Japan), IAI (Israel), OHB (Sweden).

 ROSCOSMOS is the state corporation established in August 2015 for a comprehensive reform of the rocket and space industry of Russia. ROSCOSMOS ensures performance of the state policy in space industry and normative regulation. ROSCOSMOS also places orders for development, production and delivery of space hardware and space infrastructural objects. Also, one of its functions is to develop international co-operation in space industry and provide conditions to use the results of the space activities for a social and economic progress of Russia.

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